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Imatinib 'Treatment Holiday' Risks Disease Progression Adapted from the NCI Cancer Bulletin, vol. 4/no. 13, March 27, 2007 (see the current issue). Results from a randomized European trial published in the March 20, 2007, Journal of Clinical Oncology (JCO) show that patients whose advanced gastrointestinal stromal tumors (GIST) are controlled with the drug imatinib (Gleevec®) risk rapid progression of disease if treatment is interrupted (see the journal abstract).
Imatinib can provide tumor control and prolong overall survival in up to 90 percent of patients with advanced GIST. The side effects of imatinib are usually mild but often chronic. Because the standard of care for GIST is to administer imatinib until tumor progression or recurrence develops, patients who experience adverse effects from the drug sometimes request a treatment interruption if their cancer is under control. However, no clinical studies have looked at whether treatment interruption is safe for these patients.
Investigators randomly assigned 58 patients who had taken imatinib for more than one year and whose disease was under control to either continuation of treatment or treatment interruption. Of the 26 patients continuing treatment, eight experienced disease progression. In the treatment interruption arm, 26 of 32 patients experienced disease progression, causing the trial to be stopped and physicians to recommend that all patients restart imatinib treatment.
Of the 26 patients in the treatment interruption arm who chose to restart imatinib, 24 again achieved tumor control. No difference in overall survival was seen between the two arms; however, explained the authors, the study was not designed to demonstrate equivalence in survival or increased resistance to imatinib after treatment interruption. They concluded that for GIST, "imatinib discontinuation…cannot be recommended in routine practice."
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